1. Field of the Invention
The present invention relates to a rotary switch type optical fiber switch for switching and connecting optical signals through a multiplicity of circuits used in the field of an optical fiber communications system, a light measuring instrument and the like.
More specifically, the present invention relates to a novel rotary switch type optical fiber switch which is realized by a multi-circuit optical fiber switch with about 200 switching circuits at maximum that is operated by switching and connecting optical fiber connectors in order to improve the optical capability and reliability of the switch, easily maintain and repair the switch and reduce the size thereof.
2. Description of the Related Art
There have been proposed rotary switch type optical fiber switches for switching and connecting optical signals through a multiplicity of circuits. U.S. Pat. No. 4,378,144 proposes an optical fiber switch for connecting optical signals using collimator lenses. U.S. Pat. No. 5,664,034 also proposes an optical communication monitor switch for connecting optical signals using collimator lenses.
Problems of the rotary switch type optical fiber switch using the collimator lenses will be examined. FIG. 9 is a side sectional view schematically showing the rotary switch type optical fiber switch. The main body of a stepping motor 12 is fixed to a disc-shaped fixed plate 3 and a rotational shaft 13 is rotatably disposed by passing through the center hole 4 of the fixed plate 3. Collimator lens mounting holes 5 to which fixed side collimator lenses 1 are disposed are formed on a circle which is concentric to the center of the disc-shaped fixed plate 3. Optical fibers 2 are fixed to the respective fixed side collimator lenses 1. A movable plate 8 is fixed to the rotational shaft 13 at a center hole 9. A movable side collimator lens 6 is disposed to the movable side collimator lens mounting hole 10 of the movable plate 8 and a movable side optical fiber 7 is connected to the movable side collimator lens 6.
Optical connection is executed by matching the optical axis of the movable side collimator lens 6 with the optical fiber 7 to the optical axis of a desired fixed side collimator lens 1 with an optical fiber 2 by rotating the movable plate 8 through a necessary angle by the stepping motor 12. In the rotary switch type optical fiber switch, it is not necessary to mechanically contact the end surfaces of the fixed side collimator lenses 1 with the fixed side optical fibers 2 with the end surface of the movable side collimator lens 6 with the optical fiber 7. Thus, this type of switch is advantageous in that there is no anxiety that the components will wear because they are not repeatedly in contact with each other and it suffices to use only one stepping motor as a driving power source. Accordingly, the structure of the switch can be simply arranged. In the switch, however, it is required not only to process the fixed plate 3 and the movable plate 8 with pinpoint accuracy and assemble the switch with precise assembling technology but also to provide a multiplicity of expensive collimator lenses with optical fibers.
The optical insertion loss in the connection depends on the matching accuracy of the end surface of a fixed side collimator lens 1 with an optical fiber 2 to the optical axis of the movable side collimator lens 6 with the optical fiber 7. On the other hand, the angular accuracy of the position where a stepping motor stops is at best xc2x10.05xc2x0. When collimator senses are disposed on a concentric circle having a radius of 50 mm, an error of xc2x142 xcexcm must be expected in the stop position of the stepping motor in a peripheral direction. When a single mode optical fiber (SMF9/125) was used and the dislocation of the optical axes between the respective collimator lenses was 42 xcexcm, the experimental value of the insertion loss measured by the inventor was about 0.65 dB including a Fresnel loss. This value is significant and cannot be ignored. Further, the collimator lenses are fixed to the mounting holes by bonding or soldering to maintain the mounting accuracy. In this case, there is a drawback in that the collimator lenses cannot be maintained and repaired because it is almost impossible to disassemble and remove them.
As described above, there are many problems to realize the rotary switch type optical fiber switch using the collimator lenses.
An object of the present invention is to provide a rotary switch type optical fiber switch capable of solving the problems of the aforesaid rotary switch type optical fiber switch by realizing a rotary switch type optical fiber switch that does not collimator lenses.
Another object of the present invention is to provide a rotary switch type optical fiber switch including lined-up sleeves disposed on a concentric circle so that the reliability of the switch can be improved and the switch can be easily maintained and repaired.
Still another object of the present invention is to provide a rotary switch type optical fiber switch having APC optical connector (optical connector having a spherical surface polished to an inclined state) parts disposed on a concentric circle.
A further specific object of the present invention is to provide a rotary switch type optical fiber switch using, as the basic components thereof, ferrules with optical fibers which are used as a part of the APC optical connector which have been completed to a high technical level and lined-up sleeves so that the switch has a connecting property as high as that of the APC optical connector.
To this end, according to one aspect of the present invention, there is provided a rotary switch type optical fiber switch, comprising a fixed side ferrule with optical fiber mounting plate assembly having a plurality of lined-up sleeves disposed on at least one concentric circle about a reference axis for supporting fixed side ferrules with optical fibers, a movable side ferrule with optical fiber assembly supporting a movable side ferrule with an optical fiber in parallel with the reference axis at a position apart from the reference axis a distance corresponding to the radius of the concentric circle and rotating about the reference axis as well as movable in parallel with the reference axis, and a movable side ferrule with optical fiber mounting plate driving unit assembly for locating the movable side ferrule at the angular position of an arbitrary lined-up sleeve of the fixed side ferrule mounting plate at a position apart from the fixed side ferrule mounting plate to thereby insert the movable side ferrule into the lined-up sleeve and connect it to one of the fixed side ferrules with the optical fibers.
In the rotary switch type optical fiber switch, the fixed side ferrule with optical fiber mounting plate assembly is arranged such that stepped holes are formed to the surface of a vertically standing flat plate member orthogonally thereto on the same concentric circle or a plurality M (Mxe2x89xa72) of different concentric circles about the center of a bearing hole formed orthogonally to the surface of the flat plate member at positions on the circle or the circles equally divided to N (Nxe2x89xa72) and the lined-up sleeves and the fixed side ferrules with the optical fibers are inserted into the Nxc3x97M pieces of the stepped holes and detachably fixed therein.
In the rotary switch type optical fiber switch, the movable side ferrule with optical fiber mounting plate assembly comprises a shaft disposed concentrically to the reference shaft and rotating and advancing/retreating passing through the bearing hole of the fixed side ferrule mounting plate assembly, and a movable side ferrule with optical fiber supporting flat plate member disposed orthogonal to the shaft, wherein L pieces (Lxe2x89xa71) of the movable side ferrules with the optical fibers are disposed to the flat plate member on the same concentric circle or a plurality M (Mxe2x89xa72) of different concentric circles about the center of the shaft so as to correspond to the stepped holes formed to the fixed side ferrule mounting plate assembly so that the extreme ends of the ferrules partially project from the surface of the flat plate member.
In the rotary switch type optical fiber switch, the numbers N of the sleeves disposed on the plurality M (Mxe2x89xa72) of different concentric circles formed to said fixed side ferrule mounting plate assembly are even, respectively, the numbers L of the movable side ferrules with the optical fibers disposed on the plurality M (Mxe2x89xa72) of different concentric circles formed to the movable side ferrule mounting plate assembly is odd, respectively, and a first group of the movable side ferrules with the optical fibers which includes L/2 pieces thereof is disposed at a position symmetrical to a second group of the movable side ferrules with the optical fibers which includes L/2 pieces thereof with its mounting angle dislocated 180xc2x0 from the position of the second group, whereby the rotary switch type optical fiber switch is arranged as an L (Mxc3x97N) rotary switch type optical fiber switch.
In the rotary switch type optical fiber switch, the movable side ferrule with optical fiber mounting plate driving unit assembly comprises a slide block supported by a base plate which supports the fixed side ferrule with optical fiber assembly so as to be movable in parallel with the reference axis, a stepping motor supported by the slide block so that the output shaft thereof is made concentric to the reference axis with the output shaft coupled with the shaft of the movable side ferrule with the optical fiber, and advancing/retreating means for moving the slide block in parallel with the reference shaft.
In the rotary switch type optical fiber switch, a latching solenoid magnet is used as an actuator for forming the advancing/retreating means of the movable side ferrule with optical fiber mounting plate driving unit assembly and the switch can perform a self-holding operation at a stroke end.
In the rotary switch type optical fiber switch, the movable side ferrule with the optical fiber can be caused to sequentially come into contact with any arbitrary fixed side ferrule with an optical fiber in such a manner that the extreme end of the movable side ferrule with the optical fiber is inserted into a lined-up sleeve hole by the backward movement of the slide block to thereby cause the extreme end of the movable side ferrule to come into contact with the fixed side ferrule with the optical fiber as well as said stepping motor is rotated a prescribed angle in a state that the extreme end of the movable side ferrule with the optical fiber is pulled out from the lined-up sleeve hole to thereby release the contact of the extreme end thereof with the fixed side ferrule.
In the rotary switch type optical fiber switch, the connecting end surfaces of the fixed side ferrules and the movable side ferrules are polished to an inclined spherical surface having an inclination of 4xc2x0 or more to a surface orthogonal to an optical axis.